Modern wireless handsets are required to interface with many peripherals to provide the diverse functionality required of modern communications. One such peripheral is a Multimedia Card (MMC) which allows storage of data from many different devices.
In wireless handsets, 3V I/O operation at 50 MHz is required to communicate with these cards. Since the application processor resides on an Ultradeep Sub Micron (UDSM) process, the I/O buffers need to be designed in these processes. However, UDSM processes do not have 3V transistors in the default mask set, interfacing to a 3V input is difficult.
Various aspects of UDSM technology are described in the article “Full Chip Verification of UDSM Designs”, R. Saleh et al., Proceedings of 1998 IEEE/ACM International Conference on Computer Aided Design, pp. 453-460, the teachings of which are hereby incorporated by reference.
It is therefore an object of the present invention to design an input buffer for a UDSM process that can interface with higher input voltages.